The objective of this project is to investigate the role of amino acids and acetylcholine as synaptic transmitters in the outer plexiform layer of goldfish and turtle retinae. The approach is multidisciplinary and will correlate results obtained from intracellular recording from horizontal and bipolar cells in response to pharmacological manipulations, assays for receptor binding to radiolabeled ligands for the amino acid transmitter candidates: L-glutamate, glycine and GABA, and localization of the receptors for these amino acids by autoradiography. Localization of acetylcholine receptors will be accomplished using a conjugate of horseradish peroxidase and alpha-bungarotoxin. It is expected that this research will answer the question as to how lateral and centripetal information is encoded in the distal retina of these vertebrates.